In recent years, in order to achieve a higher breakdown voltage, a lower loss, and a use under a high temperature environment for a semiconductor device such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), silicon carbide is employed increasingly as a material constituting the semiconductor device. Silicon carbide is a wide band gap semiconductor having a band gap larger than that of silicon, which has been conventionally and widely used as a material for semiconductor devices. Hence, by adopting silicon carbide as a material for a semiconductor device, the semiconductor device can have a high reverse breakdown voltage, reduced on-resistance, and the like. Further, the semiconductor device thus adopting silicon carbide as its material has characteristics less deteriorated even under a high temperature environment than those of a semiconductor device adopting silicon as its material, advantageously.
For example, “Semiconductor SiC Technology and Applications, the Second Edition” by Hiroyuki Matsunami and other three persons., Nikkan Kogyo Shimbun, Ltd., Sep. 30, 2011, p 358 to 365 (NPD 1) discloses a planar MOSFET including an insulating film, which is arranged so as to surround a gate electrode, and a source electrode interconnection, which is provided in contact with the insulating film and electrically connected to an n+ region.